In winter 1917, the French freighter Mont Blanc, laden with picric acid and TNT destined for the European war effort, headed into the great harbor of Halifax to join a convoy bound for Bordeaux. A Norwegian ship, the Imo, was leaving Halifax at the same time, destined for New York. Its mission was to bring food and supplies back to people in German-occupied Belgium and northern France.

On that cold December day, it should have been an ordinary passing of two ships. But as a result of miscommunication, navigational protocols were violated. Seamen, civilians and members of the Royal Naval College of Canada looked on in horror as the Mont Blanc and the Imo collided. The impact caused a fire on the French ship that eventually caused its explosive payload to ignite. For Haligonians, all hell broke loose. As well as destroying much of the harbor, the resulting blast killed almost 2,000 people. The captain of the HMCS Acadia, located 24 kilometers (15 miles) outside of Halifax that day, estimated the smoke rising from the seat of the explosion to be more than 3 kilometers high.

The Halifax disaster was the largest man-made explosion on Earth until World War II, when the United States' atom bombs destroyed Hiroshima and Nagasaki in 1945.

The small German population of Nova Scotia came under attack as the slogan "Place the Blame" riled people toward vengeance. Because who else could be responsible for the calamity besides the Kaiser? And weren't all Germans, therefore, collectively culpable? At first, reports emerged of rampaging crowds stoning neighbors with German-sounding names. But less than a week after the explosion, before the fires were even put out or all the bodies recovered, let alone buried, the Canadian military ordered the arrest of every German citizen.

Collective guilt is all too common throughout history, regardless of whether punishment is meted out because of political, economic or religious differences. The Jews, cruelly oppressed by Pharaoh. The Christians, persecuted by Nero. Non-Catholics on the Iberian Peninsula, tortured by inquisitors, and the reverse: Catholics, tormented by Oliver Cromwell. The consequences of collective blame and punishment — people leaving their homes en masse in search of freedom and safety — are also familiar. We see them today as people flee Afghanistan, Iraq and Syria, and as refugees flood into Europe or knock at America's door. Can looking back inform our present and mitigate the problems ahead?

A Breach of Trust

Throughout the millennia, the human family has responded to crises of citizenship and migration in different ways, particularly when religion seemed to lie at the heart of them. Exodus chapters 7-11 detail negotiations between Pharaoh and Moses as the prophet seeks freedom for his people; Pharaoh promises to release them, and reneges. In return God sends plagues, collectively punishing the Egyptians, and hatred for the Hebrews rises. Moses restates his case, and eventually, after a bloodbath of Egyptian firstborns, the Red Sea parts. For those migrants, it was the beginning of a perilous 40-year trek across Sinai. The book of Joshua recounts that when finally they arrived at their destination, the Divine instructed them to destroy the city of Jericho and all of its inhabitants. Alas, the story of migrants leaving disaster behind, only to carry it with them to a new place, is as old as the River Jordan.

Another famous story of flight from religious persecution arose in the 15th century, when Andalucia — an 800-year-old, Muslim-majority civilization on the Iberian Peninsula — fell to Catholic invaders from the north. Jewish and Muslim converts to Catholicism were brought before a tribunal of inquisitors bent on flushing out religious heretics. Their torture tactics are legendary. In 1492, King Ferdinand and Queen Isabella enacted a charter ordering the "Jews and Jewesses of our kingdoms to depart and never to return or come back to them or to any of them." Men and women whose ancestors had lived there for hundreds of years were given three months "to dispose of themselves, and their possessions, and their estates," and to leave with royal safeguard. About 165,000 people immigrated to Europe and North Africa. Some 20,000 of them died as they searched for new homelands, a statistic that brings to mind the perilous journeys of migrants who have fled Africa and Asia over the past three years.

Migrant Jews streaming south across the Mediterranean in 1492 joined a diverse religious population that included Jews who came after the First Temple in Jerusalem was destroyed in 586 B.C., Christians who came in the first and second centuries in the wake of Jesus' disciples, and Muslims who arrived with the expansion of the Islamic empire in the seventh century. What may have been lost from the multiconfessional society of Andalucia was resurrected along the southern Mediterranean. For 450 years these cultures co-mingled, until a backlash against the creation of the State of Israel resulted in the expulsion of Jews from many Arabic-speaking, Muslim-majority nations.

As for Spain, it finally revoked the Edict of Expulsion banishing Jews in 1968, after the Second Vatican Council decreed in the seminal document "Nostra aetate" that,

"what happened in [Jesus'] passion cannot be charged against all the Jews, without distinction, then alive, nor against the Jews of today. Although the Church is the new people of God, the Jews should not be presented as rejected or accursed by God, as if this followed from the Holy Scriptures."

The Germans of Halifax were slowly exonerated after the captain of the Mont Blanc was arrested and charged with manslaughter. (The charges against him were later dropped for lack of evidence.) But trauma within their community remained. In addition to experiencing the fires, tsunami and deaths that followed the Mont Blanc explosion, the trust of neighbors had been breached.

A Global Ethic

How might nations today avert collective blame and punishment while finding the right balance between security and compassion? What constitutes the legitimate control of borders? How do we vet perfect strangers and identify the atypical threats? How do we articulate our moral and ethical stances to reflect respect for where we come from, what our nation is today and what it may someday become? With cooperation and trust, advises Jeffrey D. Sachs in his 2011 book, The Price of Civilization: Reawakening American Virtue and Prosperity:

"Many of our major global problems — climate change, global population growth, mass migration, regional conflicts, and financial regulation — will require a much higher level of political cooperation among the world's major powers than we have so far achieved. Without sufficient trust across national borders, the growing global competition over increasingly scarce resources could easily turn into great power confrontations. Without trust, there is little chance for the coordinated global actions needed to fight poverty, hunger, and disease. Without trust, governments will be at the mercy of footloose global corporations that move their money to tax havens around the planet and pressure governments to lower tax rates, labor standards, environmental controls, and financial regulations. Mindfulness of the world therefore really amounts to a new readiness to adopt global norms of good behavior that aim to protect poor countries as well as the rich, weak countries as well as the powerful."

Today's growing global trend toward nativism evidences lack of trust, competition for resources and blindness to the wisdom of the elders, prophets and ethicists. Theologian Hans Kung would argue that our norms must include inclusivity, that "there will be no better global order without a global ethic." Kung drafted the Declaration Toward a Global Ethic for the Parliament of the World's Religions in 1993:

"By a global ethic we do not mean a global ideology or a single unified religion beyond all existing religions, and certainly not the domination of one religion over all others. By a global ethic we mean a fundamental consensus on binding values, irrevocable standards, and personal attitudes. Without such a fundamental consensus on an ethic, sooner or later every community will be threatened by chaos or dictatorship, and individuals will despair."

The consensus should include the sustainable treatment of the natural environment, the rule of law, distributive justice and solidarity, and the core value of mutual esteem.

But long before Sachs and Kung, the founders of the United States maintained an ethical sensibility made manifest in the Bill of Rights. The founders, with Bibles and Korans in their libraries, were cognizant of the religious persecutions of the past — including instances of religious tyranny in pre-colonial and colonial times. They chose to guard citizens' right to worship in different ways by preventing the "misconstruction or abuse" of congressional powers.

It wasn't easy coming up with the words to describe the rights that would protect and dignify the people of a nascent nation. James Madison's original provision on religion read: "The civil rights of none shall be abridged on account of religious belief or worship, nor shall any national religion be established, nor shall the full and equal rights of conscience be in any manner, or on any pretense, infringed." The House of Representatives altered the text to read: "Congress shall make no law establishing religion, or to prevent the free exercise thereof, or to infringe the rights of conscience." The Senate then refined it even further to say, "Congress shall make no law establishing articles of faith, or a mode of worship, or prohibiting the free exercise of religion." In 1791 — three years after the Constitution was ratified — the First Amendment was finally adopted:

"Congress shall make no law respecting an establishment of religion or prohibiting the free exercise thereof; or abridging freedom of speech or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances."

Ours is the oldest written constitution still in use. Its checks and balances have safeguarded democracy for nearly 230 years. The establishment and exercise clauses keep a wall of sanctity between religion and state. This system is one with enough flexibility to grow gracefully with our nation's changing political, economic and cultural norms. And it may see its mettle tested in the coming years, particularly if the question of registering people according to their religion is pursued.

Unlike the forced diaspora of Jews from the newly Catholic Spain, the fate of Nova Scotia's innocent Germans, and the Muslim victims of the Islamic State, the United States will not sanction collective punishment — the establishment and exercise clauses proscribe such retribution on religious terms. Religious affiliation is not listed on the country's national census or on American passports. Thanks to the First Amendment, it's really nobody's business what faith a person practices. Someday the strengths of the American dream may go global. Someday nations may sign up for Kung's dream of a global ethic. At the very least, as Sachs exhorts, "We need to return to a spirit of true deliberation at all levels of society, one that reconceives politics as honest group problem solving, grounded in mutual respect and shared values."